Field of the Invention
The invention relates to a data transmission method using LT code.
Description of Related Art
Along with development of network technology, various digital data on network is generated and accumulated in an amazing speed. Through the Internet of things, streaming data generated in real-time further relies on analysis and application provided through high quality communication transmission. Luby transform code (LT Code) is easy to be implemented through software due to its low computation complexity, and when it is implemented in an existing system, it is unnecessary to add too much hardware cost. Since the number of users using a video streaming service is continually increased, to use the LT Code technique to improve image transmission quality is an expected value-added service option.
The LT Code is an error correction coding method used for the image streaming service, and main characteristics thereof are the low computation complexity and rateless, and regarding a packet error or packet loss occurred during the transmission process, it has a mechanism of directly correcting the error without requiring a sending node to resend the packet.
In a coding process of the LT Code, the sending node may divide the data to be sent into K source symbols with a fixed size, and select an arbitrary number (which is greater than 0 and smaller than or equal to K) of the source symbols from the K source symbols to perform encoding, so as to generate encoded symbols for sending. The sending node may repeatedly execute the aforementioned step to generate a plurality of encoded symbols for sending to a receiving node until the receiving node decodes the source symbols. A degree value can be defined as the number of the source symbols contained in one encoded symbol, and can also be defined as the number of the source symbols connected to one encoded symbol. Each degree value i corresponds to a probability, which represents a chance that the degree value i is selected to use i source symbols to generate one encoded symbol, where i and K are all positive integers, and i is greater than 0 and is smaller than or equal to K. A set of probabilities corresponding to all of the degree values (i.e. 1-K) can be referred to as a degree distribution. The degree distribution can be defined as Ω={Ωd; d=1, 2, . . . K}, where Ωi is the probability corresponding to the degree value i.
However, the key of good or bad encoding performance of the LT Code lies in a design of the degree distribution. Selection of the degree distribution may influence a decoding performance of the receiving node, which is an important factor that determines whether the receiving node can successfully decode the original data sent by the sending node. In the prior art, the degree distribution is deduced based on larger encoded blocks. However, in an actual application, the smaller encoded blocks have an unexpected effect due to increase of variability caused by a random function.